Bituminous compositions containing high molecular weight ethylene/propylene copolymer

ABSTRACT

Bituminous compositions having improved impact strength at both high and low temperatures comprise asphalt and an ethylene/propylene copolymer having a molecular weight from about 50,000 to about 100,000.

United States Patent Raley, Jr.

[ 51 June 13, 1972 [54] BITUMINOUS COMPOSITIONS CONTAINING HIGHMOLECULAR WEIGHT ETI-IYLENE/PROPYLENE COPOLYMER [72] Inventor: CharlesF. Raley, Jr., Midland, Mich.

[73] Assignee: The Dow Chemical Company, Midland,

Mich.

[22] Filed: June 18, 1969 21 App]. No.: 834,543

[52] us. Cl. ..260/28.5, 260/285 A [51] Int. Cl ...cosr 45/52, C09d 3/6058 Field of Search 260/28.5 AS

[56] References Cited UNITED STATES PATENTS 3,070,557 12/1962 Gessler etal 269123.; A

3,093,60l 6/1963 Gessler et al ..260/28.5 A

FOREIGN PATENTS OR APPLICATIONS 1,368,242 6/1964 France PrimaryExaminerMorris Liebman Assistant Examiner-Samuel L Fox AttorneyGriswold& Burdick, L. J. Dankert, R. 0. Waterman and M. S. Jenkins [57] ABSTRACT6 Claims, No Drawings BITUMINOUS COMPOSITIONS CONTAINING HIGH MOLECULARWEIGHT ETHYLENE/PROPYLENE COPOLYMER BACKGROUND OF THE INVENTION Thisinvention relates to improved bituminous compositions and particularlyto bituminous compositions useful as roofing materials, adhesivematerials and the like.

Asphalt and other bituminous materials have been widely utilized in theconstruction of roads, in the production of roofing materials and likeprotective coatings, as adhesive materials and the like. Unfortunately,however, such materials tend to deteriorate under conditions of extremetemperature variations, constant exposure to physical stress and variousweather agents.

In order to overcome these deficiencies in the properties of thebituminous materials, particularly asphalt, it has been a practice inthe art to blend various rubbers, particularly the styrene-butadienerubbers, with the asphalt. It is found, however, that the unsaturatedstyrene-butadiene rubbers become oxidized, especially when exposed tohigh temperatures, and as a result lose many of their desirableproperties such as elasticity, impact strength and the like. It has alsobeen a practice to incorporate various polyolefins into asphalt toimprove elasticity and impact strength. Unfortunately the polyolefinsstiffen the resulting compositions which often causes poor lowtemperature flexibility. Such compositions, particularly in moistureladen areas, become brittle and are subject to cracking and crumblingupon exposure to extremely low temperatures.

More recently the incorporation of low molecular weightethylene/propylene copolymers into asphalt has been found to improve lowtemperature flexibility somewhat. In some instances, however, such lowmolecular weight ethylene/propylene copolymers actually lower the impactstrength of the asphalt. Also, some low molecular copolymers tend toflow at temperatures as low as 100 F; and as a consequence, blends ofasphalt and the low molecular weight copolymers do not retain theiroriginal shape or uniform composition.

In view of the aforementioned problems it would be highly desirable toprovide a bituminous composition which has good physical properties atboth high and low temperatures.

SUMMARY OF THE INVENTION In accordance with the present inventionbituminous compositions having improved flexibility and impact strengthover a wide range of temperatures are provided by blending together fromabout 99 to about 50 weight percent of a bituminous material with fromabout I to about 50 weight percent of an ethylene/propylene copolymerhaving a molecular weight from about 50,000 to about 100,000.

The resulting bituminous compositions are particularly useful as roofingcompositions, protective coatings, sounddeadening coatings,water-repellant coatings, adhesives and the like. In addition, thesenovel compositions can be blended with sand, gravel and the like to formexcellent paving and construction materials.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By the term bituminousmaterials" is meant the many petroleum and like mineral residues rangingfrom those derived from petroleum (asphaltic products) to those derivedfrom coal tar. The asphaltic products include native asphalts, residualasphalts, blown petroleum asphalts precipitated by propane and the like.The tar products include pitch obtained as a residue by the removal ofvolatile oils from coal tar by distillation as well as combinationsthereof with oil, gas tar, and water gas tar. These materials areprovided in the form of semi-liquids to semi-solids. The same groups ofsubstances are also commonly prepared with a harder consistency and alsowith a higher fusing point. The latter materials are used primarily ascoating or adhesive compositions. These and other bituminous materialsare useful in the present invention. Preferred bituminous materials arethe various types of asphalts such as the naphthenic and aromatic typeswith the naphthenic types being especially preferred.

Ethylene/propylene copolymers suitable for the purposes of thisinvention advantageously contain from about 10m about 70 weight percentof polymerized ethylene and from about to about 30 weight percent ofpolymerized propylene, preferably from about 40 to about 50 and fromabout 60 to about 50 weight percent, respectively. However, copolymerscontaining less than 10 weight percent and more than 70 weight percentof ethylene are operable. It is understood, however, that small amounts,i.e., up to about 5 weight percent, of other comonomers such as butene-lhexene-l pentene-l and other alpha olefins or crosslinking comonomerssuch as 1,5-hexadiene, divinyl benzene, ethylidene, norbornene and thelike can optionally be present in the above described copolymers. Suchsuitable copolymers are amorphous polymers having molecular weights fromabout 50,000 to about 100,000, preferably from about 50,000 to about80,000. The high molecular weight copolymers suitable for use in thisinvention are readily prepared by contacting olefin mixtures containingfrom about 99 to about 75 weight percent of propylene and from about 1to about 25 weight percent of ethylene with a metallic catalyst, e.g., aZiegler or Phillips-type catalyst, dissolved in an inert liquid such asan aliphatic hydrocarbon. Generally such polymerizations are carried outin an inert atmosphere and at relatively low temperatures and pressures.It is understood that other known methods for producingethylene/propylene copolymers having molecular weight in the specifiedrange are also suitable. During the preparation of the high molecularweight copolymer, a certain amount of low molecular weight material,i.e., less than 50,000, is often produced. It is generally preferable toremove the low molecular weight copolymer by recrystallizing the highermolecular weight copolymer, i.e., greater than 50,000 and generally lessthan 100,000, from inert hydrocarbon solvents such as pentane. Theresulting higher molecular weight ethylene/propylene copolymer is arandom copolymer wherein the propylene and ethylene'molecules arerandomly dispersed throughout the polymer chain.

In addition to the above-described essential ingredients, optionalingredients such as mineral aggregates, cement, sand, asbestos,vermiculite, fiberglass and the like may also be included in thebituminous compositions of the present invention.

The bituminous material is suitably blended with the ethylene/propylenecopolymer by any of several well known methods for blending asphaltmaterials with various rubbers and the like. For example, theethylene/propylene copolymer can be placed on a hot-roll mill followedby the portionwise addition of the bituminous material until the desireddilution is obtained. In another technique, the copolymer is fluxed intoa portion of the molten asphalt, and when a homogenous mixture isobtained, the balance of the asphalt is added.

The resulting blends of this invention contain from about 99 to about 50weight percent of the bituminous material and from about 1 to about 50weight percent of the ethylene/propylene copolymer, preferably fromabout 99 to about 75 weight percent and from about I to about 25 weightpercent respectively.

The following examples are given to illustrate this invention and shouldnot be construed as limiting its scope, In the specification and claimsall parts and percentages are by weight unless otherwise indicated. Inaddition, all melt flow viscosities are determined according to ASTMD-l238-65 T(E).

EXAMPLE I A SO-part portion of an ethylene/propylene copolymer (40/60)having a melt flow viscosity of 0.7 decig/min. (MW 51,000) is plastifiedon a hot-roll mill at C. To the plastified copolymer is added 50 partsof a naphthenic type asphalt. Additional amounts of the asphalt are thenblended with several samples of the resulting mixture at 100 C toproduce blends having concentrations as specified in Table l. Thevarious blends are melt-coated on aluminum panels (4 inches X 2 inches0.019 inch) and stored overnight at -1 8 C. The panels are then quicklyflexed while cold. The degree of cracking and adhesion are given inTable I.

For the purposes of comparison, a control sample (C,) of the naphthenicasphalt used above is similarly applied to an aluminum panel, storedovernight at -l8 C and tested as described above. The results of thetest are also shown in Table I.

" Not an example of this invention l S no cracking, elastic and goodadhesion after flexing at l 8 C.

l cracking, extensive splintering, brittle and poor adhesion uponflexing at l 3 C.

EXAMPLE 2 An ethylene/propylene copolymer (40/60) having a melt flowviscosity of 0.2 decig/min. (MW 65,000) is blended with various amountsof the asphalt of Example I. The resultant blend samples are cast fromhot melt at 200-240 C to form test tabs (2% inches X '1; inch X /8inch). The test tabs are placed on two supports spaced 1% inches apartand tested for impact resistance at l 8 C. The impact resistance testingdevice is basically a pivotal arm rotably mounted to a stationary membersuch that the point of impact occurs when the pivotal arm is onhorizontal plane. The impact is increased merely by releasing thepivotal arm at a greater elevation from the point of impact. The resultsof the impact resistance tests are shown in Table I].

For the purposes of comparison and to particularly point out theadvantages of this invention, an ethylene/propylene copolymer (52/48)having a melt flow viscosity of 52 decig/min. (MW 24,000) is blendedwith various amounts of the asphalt used above. The resultingcomparative samples D D and D are cast from hot melt at 200-240 C toform test tabs (2% inches X 86 inch X /6 inch) which are tested forimpact resistance by the method described above. The results are shownin Table ll.

Also for the purposes of comparison a control sample (C containing onlythe asphalt described above is tested for impact resistance and theresults are likewise shown in Table ll.

' Not an example of this invention (1) HMWC High molecular weightethylene/propylene copolymer (65,000).

LMWC Low molecular weight ethylene/propylene copolymer (24,000).

(2) Each value of impact resistance is given as the weighed averageforce required to break four test tabs.

EXAMPLE 3 In a manner similar to Example 2 samples (7 and 8),comparative samples (D and D and a control sample (C are prepared usingan aromatic asphalt instead of the naphthenic asphalt of Example 2. Thesame higher molecular weight ethylene/propylene copolymer used in thesamples (4, 5 and 6) of Example 2 is used in samples (7 and 8). The samelow molecular weight copolymer used in the comparative samples (0,, Dand D of Example 2 is used in the comparative sam ples (D and D Theresulting blend samples and control sample are formed into test tabs andtested for impact strength by the procedure used in Example 2. Theresults of these tests are shown in Table III.

TABLE III Sample Ingredients Impact Resistance No. Asphalt HMWC LMWC l0ergs D 99 O l 2.28

Not an example of the invention 1-2 Same as in Table ll.

As evidenced in Table [I] an increase in the high molecular weightethylene/propylene copolymer concentration from 1 to 10 percent resultsin an increase in impact resistance. In contrast thereto, an increase inlow molecular weight ethylene/propylene copolymer concentration from Ito 10 percent results in a decrease in impact resistance.

EXAMPLE 4 A 50-part portion of the ethylene/propylene copolymer ofExample 2 is plastified with a hot mill at C. To the plastifiedcopolymer is added a SO-part portion of the aromatic asphalt of Example3. Additional amounts of the asphalt are then blended with severalsamples of the resulting mixture heated to 100 C to produce blendsamples having concentrations as specified in Table IV. The blendsamples (9, l0 and 11) are compression molded into test tabs (2% inchesX ,5 inch X /6 inch) at temperatures less than l50 C and tested forimpact strength by the procedure described in Example 2. The results ofthese tests are recorded in Table IV.

For the purposes of comparison, an ethylene/propylene copolymer (40/60)having a melt index of 60 decig/min. (MW 23,000) is blended with variousamounts of the asphalt described above. These resulting comparativeblend samples (D D and D are compression molded into test tabs by theabove procedure. In a similar manner, other comparative blend samples (DD and D) are prepared using an ethylene/propylene copolymer (40/60)having a melt index of 6.3 decig/min. (MW 33,400) and theabove-described asphalt, molded into test tabs and tested for impactstrength. Test tabs of a control sample (C,) containing only the asphaltare similarly prepared and tested. The results of these tests arerecorded in Table IV.

D, 95 5 1.66 D 90 10 1.32 D, 99 l 0.33 D 95 s 0.15 o 90 10 3.28 100 0.84

' Not an example of the invention (1) HMWC High molecular weightethylene/propylene copolymer (MW 65 .000).

LMWC(a) Low molecular weight ethylene/propylene copolymer (MW=23,000)

LMWCOJ) Low molecular weight ethylene/propylene copolymer (MW 33,400)

(2) Same as in Table [1.

1. An asphalt composition having improved flexibility and impactstrength over a wide range of temperatures which comprises (I) fromabout 99 to about 50 weight percent of an asphalt material and (2) fromabout 1 to about 50 weight percent of an ethylene/propylene copolymerhaving a molecular weight ranging from about 50,000 to about 100,000.

2. An asphalt composition according to claim 1 wherein the copolymercontains from about 10 to about 70 weight percent of polymerizedethylene and from about to about 30 weight percent of polymerizedpropylene.

3. An asphalt composition according to claim 1 wherein the copolymer hasa molecular weight ranging from about 50,000 to about 80,000.

4. An asphalt composition according to claim 1 wherein the compositioncontains from about 99 to about 75 weight percent of the asphaltmaterial and from about I to about 25 weight percent of the copolymer.

5. A bituminous composition according to claim 4 wherein the copolymercontains from about 40 to about 50 weight percent of polymerizedethylene and from about 60 to about 50 weight percent of polymerizedpropylene.

6. A bituminous composition according to claim 1 wherein the bituminousmaterial is asphalt.

2. An asphalt composition according to claim 1 wherein the copolymercontains from about 10 to about 70 weight percent of polymerizedethylene and from about 90 to about 30 weight percent of polymerizedpropylene.
 3. An asphalt composition according to claim 1 wherein thecopolymer has a molecular weight ranging from about 50,000 to about80,000.
 4. An asphalt composition according to claim 1 wherein thecomposition contains from about 99 to about 75 weight percent of theasphalt material and from about 1 to about 25 weight percent of thecopolymer.
 5. A bituminous composition according to claim 4 wherein thecopolymer contains from about 40 to about 50 weight percent ofpolymerized ethylene and from about 60 to about 50 weight percent ofpolymerized propylene.
 6. A bituminous composition according to claim 1wherein the bituminous material is asphalt.